Training-pertamina Well Logging

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COURSE OBJECTIVES

• Open hole Logging:

– Learn the basic tool theory, data acquisation, LQC, applications and limitations of commonly used open-hole logging tools. (SP, GR/NGS, Resistivity laterolog/induction, neutron porosity,

sonic, density, RFT/MDT, SHDT/FMI)

– Learn how to correct log readings for the effect of invasion, hole and environment. And make quantitative analysis of log readings.

– Do quantitative log analysis through in-class example, work sessions.

– Able to predict the location of potential hidrocarbon zone and predict producibility

• Basic Log Interpretation

– Learn the basic concept of log interpretation. (Archie formula, clean sand quick-look, dual water model concept,)

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INTRODUCTION

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JENIS LOGGING YANG UMUM

•• OPEN HOLE LOGGING SERVICES

OPEN HOLE LOGGING SERVICES

– Wireline Logging: Resistivity, GR, Density, Porosity, FMI, RFT/MDT, CMR/NMR, Check shot, VSP.

– LWD: Resistivity, Porosity,density, Sonic, RAB, Seismic while drilling, dll.

•• CASED HOLE LOGGING SERVICES

CASED HOLE LOGGING SERVICES

– Formation Evaluation: Resistivity, Porosity, Pressure, fluid analysis and samples, RST.

– Production & Monitoring: Perforation, CBL/CET, Production Logging Tools, Casing Evaluation, dll.

•• OTHERS SERVICES

OTHERS SERVICES

– Subsidence monitoring, Back-off, SIT, Cutter, Packer setting, dll.

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WHAT CAN BE EX

WHAT CAN BE EXP

PECTED

ECTED

FROM LOG DATA??

ALL LOGS LOOK THE SAME.

Although two logs may appear similar,

the information content and validity could vastly differ.

Hydrocarbon volume= 7.758 X Φ X (1-Sw) . h. A

What logging tools do you want to use to meet your objectives ??

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BAGAIMANA VALIDITAS DARI DATA

BAGAIMANA VALIDITAS DARI DATA??

??

(Log Quality Control)

• Pengaruh environment terhadap alat logging saat pengukuran dilakukan?

• Dinding sumur? caving? Rugousity? ovality?lumpur? Kecepatan logging? Yoyo effect? Bed boundary?

• Ke-akuratan pengukuran ? • Batas-batas pengukuran

• Pengukuran alat ukur ‘kedalaman’ atau depth system apakah bekerja dengan baik? Sampai dimana

ke-akurat-an nya?

• Apakah response dari tools di zona interest tepat dan bisa dipercaya?

• Apakah datanya di- filter? Filter apa yang dipakai? Parameter yang dipakai? ?

• Apakah ‘kalibrasi’ nya tepat dan bisa dipercaya? • Dimanakah ‘centralizer’ atau ‘de-centralizer’?nya

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FUNGSI DARI DATA LOG ??

• Untuk Geologist?

– Kedalaman top formasi, Ada Hydrocarbon? Minyak/gas? Komersial?lingkungan pengendapan cocok unt HC? kemiringan lapisan? Bagaimana dg kemungkinan offset wells? Type clay nya apa? Dll.

• Untuk Reservoir Engineer?

– Ketebalan dari pay zone? Apakah reservoir homogen? Driving mechanismnya? Permeability? Pressure? Volume HC? Dll.

• Untuk Geophysicist ?

– Apakah Top formasi sesuai dengan prediksi? Apakah zona interestnya sesuai dg prediksi seismic? Bagaimana sintetic seismogramnya? Kecepatan suara di tiap lapisan? Dll.

• Untuk Production Engineer? Drilling Engineer? • Petrophysicist?

BAGAIMANA DENGAN DECISION MAKER??

ATAU BUYERS?? DALAM MEMILIH LOGGING TOOLS YANG TEPAT, EFFISIEN DAN EKONOMIS

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SPONTANEOUS POTENTIAL (SP)

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Symbols Used in Log Interpretation

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Electrokinetic Potential of SP

PROSES TERJADINYA SP

Electrochemical membrane potential of SP

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Figure B9

The SP Circuit Path

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CONTOH LOG SP

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The SP Deflection and its R

_mf

- R

_w

Dependency

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• The SP log is used for:

– Differentiate potentially porous and permeable reservoir rocks from impermeable clays.

– Define bed boundaries

– Give an indication of shalliness (Max deflection is clean minimum is shale) – Determine Rw in both salt and fresh

muds.

PENGGUNAAN LOG SP

• Factors effecting SP reading

– Bed thickness – Invasion profile – Tight formation – Noise

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GAMMA

GAMMA--RAY &

RAY &

NATURAL GAMMA

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M axi m u m D e fl ect io n M in imu m D e fl e c tio n

GAMMA-RAY

• The Gamma-Ray log is a measurement of the formation’s natural radioactivity ( total from Potassium, Uranium, Thorium).

• The tool reacts if the shale is radioactive (usually the case), hence show the sands and shales, the permeable zones and the non-permeable zones. • Computation of the amount of shale: The minimum

value gives the clean (100%) shale free zone, the maximum 100% shale zone.

• The Gamma-ray log is used for:

– Lithology/Mineralogy (e.g. shalliness) – Correlation

– Subsidence logging – Tacer logging

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NATURAL GAMMA

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NATURAL GAMMA-RAY

• The Gamma-Ray log is a measurement of the spectrum that is the result of the three naturally (Potassium, Uranium, Thorium) occuring

radioactive series that presents in the formation. • The Natural Gamma-ray log is used for:

– Lithology/Mineralogy (e.g. shalliness) identification – Study of depositional environtment

– Investigation of shale type

– Correlation of the GR for clay content evaluation. – Identification of organic material and source rocks. – Fracture identification

– Geochemical logging

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NEUTRON POROSITY TOOL

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BASIC MEASUREMENT

Time (m/s) Gamma-ray emmited Captured

Average thermal energy 0.025 ev Epithermal region

Energy leaving source AmBe Source Chemical (16 Mev) H Fast Neutron Slowed Neutron Fast Fast Neutron Fast Neutron

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• CNT measures the neutron population in the thermal region- The tool measures the

Hydrogen Index which is the quantity of the Hydrogen per unit volume.

• CNT is used to measure porosity

• Combined with the bulk density, it gives the best possible answer for lithology and

porosity interpretation.

• It can be used in cased hole.

• The logs have to be corrected for the borehole environtment such as:

– Borehole size, Mud cake, Borehole salinity, Mud

weight, Temperature, Pressure, Formation salinity, Stand-offs.

Fresh Water

COMPENSATED NEUTRON TOOLS (CNT)

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LITHO DENSITY TOOL

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LDT Basic Measurement

• The LDT has a chemical gamma-ray

source and two detectors. It uses gamma-ray interactions in the Compton Scattering energy range to measure the bulk density of the formation.

• The reaction is when the incident gamma-ray reacts with an electron deflecting it from its path and losing energy in the process.

• The number of gamma-ray returning to the detector depends on the number of

electron present, the electron density.

• The electron density can be related to the bulk density of the minerals by simple

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LDT Basic Measurement (Con’tinue...)

• The tool uses two detectors, the long

spacing- makes the primary measurement • LDT is a pad tool with collimated source and

detectors. It experiences little or no

environmental effect (Note: Hole rugosity may affect the measurement)

• The short spacing is used to correct the

result for near borehole effects, such as mud-cake and rugosity.

• The output are:

– Rhob (The correct bulk density) – PEF

– Drho ( The correction that has been applied to Rhob- quality curve)

• The photoelectric effect occurs when the incident gamma-ray is completely absorbed by the electron- the energy expelling the electron from its atom and this related to the lithology.

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DENSITY TO POROSITY CONVERTION DENSITY TO POROSITY CONVERTION

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BULK DENSITY CONVERTION TO POROSITY BULK DENSITY CONVERTION TO POROSITY

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INTEGRATED POROSITY LITHOLOGY

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SONIC POROSITY

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BASIC MEASUREMENT

• The Sonic tools create an acoustic signal and measure how long it takes to pass through a rock.

T1 T2 R2 R1 R3 R4 R e ci evers T

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SONIC TOOLS SUMMARY

Measurement BHC LSS SDT DSI Compresional X x x x Shear/stonely: Hard rock - - x x Soft rock - - x Computations: Porosity x x x x Lithology x x x x Seismic tie in x x x x Mech. Properties: Hard rock - - x x Soft rock - - x Fracture detection - - x x Permeability - - x

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TYPICAL

LOG

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LITHOLOGY IDENTIFICATION

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RESISTIVITY LOG

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V

I

BASIC MEASUREMENT

The resistivity (r) of substance is a measure of its Ability to impede the flow of electrical current

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Symbols Used in Log Interpretation

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DUAL LATEROLOG TOOL

• DLL tool ha response range of .2 to 40,000 ohm-m.

• The deep laterolog measurement (LLD) has a deeper depth of

investigation of about 1.2 to 1.5m and vertical beam current of 2f.

• The shallow laterolog measurement (LLS) has about 50 to 60 cm and vertical beam current of 2f.

• Dual laterolog performs most

effectively in saline mud (Rmf/Rw < 2.5)

• RLL = Rm + Rmc + Rxo + Rt • Combined with MSFL to get Rt

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MICRO SPHERICALLY LOG

• The MicroSFL is a pad mounted spherically focused logging device. The tool measure resistivity in the invaded zone.

• MSFL forcing the measurement current to flow directly into the formation, the effect of mud cake resistivity on the tool response is minimized.

• MSFL is combinable with Dual laterolog or Induction log.

• The application of MSFL log are:

• Identification of permeable zones.

• Measure Rxo

• Sw determination using Rxo and

Rt values provide an independent lithology-free check on other

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Basic two-coil induction log system

DUAL INDUCTION TOOL

• How to measure resistivity of the formation in fresh mud or oil base mud where dual laterolog will not work?

• Induction tool uses a high frequency “e.m” transmitter to induce a current in a ground loop of formation- this, in turn, induces electrical field whose magnitude is proportional to the formation conductivity.

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F

igur

e B

1

Cm Cmc Cxo _Ct

• Induction tools measure Conductivity.

• Induction tools measure resistivity in Parallel

• Best readings occur in high resistivity mud, oil-based is better, fresh mud is good

• Induction Corrections: •Borehole effect

•Shoulder bed effect

•Skin effect (Caused by ground loops creting their own fields

and interfering with the signal being measured)

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F

igur

e B

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PERBANDINGAN LOG

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Array Induction Tool

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HIGH RESOLUTION DUAL LATEROLOG

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PEMILIHAN RESISTIVITY TOOL

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MODULAR DYNAMIC TESTER

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MDT APPLICATIONS

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Picture B14

CASED HOLE MDT

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FORMATION MICRO SCANNER

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FRACTURE

FRACTURE IDENTIFICATION

IDENTIFICATION

RESISTIVITY LOG

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F igur e B 1 5

FMI EXAMPLES

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CASED HOLE RESISTIVITY

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PEMAKAINAN NMR DI DUNIA KEDOKTERAN

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CMR

( COMBINABLE NUCLEAR MAGNETIC RESONANCE

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NUMAR/MRIL

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MRIL TOOL PRINCIPLES

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MRIL TOOL RESPONSE

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BASIC QUICK

BASIC QUICK--LOOK INTERPRETATION

LOOK INTERPRETATION

• Quick-look methods of log interpretation might be clasiied as those used to identified possible producing zones, usually at the wellsite. The requirement are to locate permeable beds, calculate bed

thickness, porositys and saturations of hydrocarbon zones, and to predict producibility.

• Methods that usually used: Overlay Technique, Rwa, Direct Method of Calculating Sw.

• Assumptions that should be considered:

– Constant Rw,

– Thick and homogenous formation, – constant clean lithology,

– a clean water bearing zone must exist,

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Rwa Technique

Basic Archie’s equation:

Assume: Sw =100%, then:

Rearrang to solve for Rw

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Water Saturation Calculation

Basic Archie’s equation:

If Ro is the resistivity when 100% water, Rt= F.Rwa or we call Rt = Ro

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